NED Abstract

Copyright by Royal Astronomical Society.
2009MNRAS.392..294A
Large-scale galactic turbulence: can self-gravity drive the observed HI
velocity dispersions?
Agertz, Oscar; Lake, George; Teyssier, Romain; Moore, Ben; Mayer, Lucio;
Romeo, Alessandro B.
Abstract. Observations of turbulent velocity dispersions in the HI
component of galactic discs show a characteristic floor in galaxies
with low star formation rates and within individual galaxies the
dispersion profiles decline with radius. We carry out several
high-resolution adaptive mesh simulations of gaseous discs embedded
within dark matter haloes to explore the roles of cooling, star
formation, feedback, shearing motions and baryon fraction in driving
turbulent motions. In all simulations the disc slowly cools until
gravitational and thermal instabilities give rise to a multiphase
medium in which a large population of dense self-gravitating cold
clouds are embedded within a warm gaseous phase that forms through
shock heating. The diffuse gas is highly turbulent and is an outcome of
large-scale driving of global non-axisymmetric modes as well as
cloud-cloud tidal interactions and merging. At low star formation rates
these processes alone can explain the observed HI velocity dispersion
profiles and the characteristic value of ~10kms^-1^ observed within a
wide range of disc galaxies. Supernovae feedback creates a significant
hot gaseous phase and is an important driver of turbulence in galaxies
with a star formation rate per unit area >~10^-3^M_sun_yr^-1^kpc^-2^.
Key words: hydrodynamics, turbulence, galaxies: evolution, galaxies:
formation, galaxies: general